The present invention relates to a linear motor which directly transforms electrical energy to linear mechanical energy. More precisely, the present invention relates to linear motors which are generally based on a same principle as a synchronous motor, having a permanent magnet as a rotator, or a brushless direct current motor. The difference is that both the primary magnetic means and the secondary magnetic means are developed linearly in the present invention.
Various linear motors of the type have been proposed as of the present time. Of these linear motors, FIGS. 10 and 11 show an example known as a double-sided linear motor wherein a synchronous motor having a permanent magnet as a rotator is developed linearly and two primary magnetic means 1a,1b are symmetrically disposed so as to hold therebetween a plate-formed secondary magnetic means 6. The primary magnetic means 1a comprises a primary core 3, having laminated iron plates forming teeth 2a and grooves 2b, and coils 4u,4v,4w disposed in the grooves 2b so as to wind around the teeth 2a.
FIG. 11 shows the primary magnetic means 1a seen from below as denoted by D--D in FIG.11. As shown in FIG. 11, the coil 4u is wound passing the first and fourth grooves 2b so as to hold the teeth 2a1,2a2,2a3 therein. The coil 4v is wound passing the second and the fifth grooves 2b so as to hold the teeth 2a2,2a3,2a4 therein. The coil 4w is wound so as to hold the teeth 2a3,2a4,2a5. Then again, coil 4u is wound so as to hold the teeth 2a4,2a5,2a6, and so on.
When a three-phase electric current is supplied to the coils 4u,4v,4w, the primary magnetic means generate a traveling magnetic field traveling along its axis in the direction shown by A or B in FIG. 10.
The secondary magnetic means 6 comprises a plurality of parallelepiped secondary cores 7 made of iron and a plurality of plate-like permanent magnets 8 connected to each other in turn in a rod-like form, FIG.10. The permanent magnets 8 are so disposed as to the direction of magnetic polarity of adjacent magnets 8 opposes to each other. In other words, an N pole of a magnet 8 faces against an N pole of an adjacent magnet 8 through a secondary core 7 disposed therebetween. An S pole of a magnet also faces against an S pole of an adjacent magnet 8 in a same manner. As a result, magnetic flux generated around the secondary magnetic means 6 flows from a core 7a sandwiched between a pair of opposing N poles to a pair of adjacent cores 7b sandwiched between a pair of opposing S poles, passing through a space outside the magnet 8. Then the magnetic flux flows from the pair of cores 7b to the core 7a through the permanent magnets 8 sandwiched therebetween.
The distance between a pair of adjacent permanent magnets 8 is identical to three times the distance between adjacent teeth 2a. A support means (not shown) is provided between the primary magnetic means 1a,1b and the secondary magnetic means 6 so as to keep the distance therebetween constant and support the primary magnetic means 1a,1b slidably against the secondary magnetic means 6.
When a three-phase current is provided to the primary magnetic means 1a,1b, the magnetic means 1a,1b generates a traveling magnetic field traveling along the axis and the primary magnetic means 6 is propelled along the axis as a result.
FIG. 12 shows another conventional linear motor which has a same primary magnetic means 1a,1b. The difference in the secondary magnetic means 12 is that pairs of permanent magnets 11 are attached to an elongated iron core 10 sandwiching the core 10 therebetween. Directions of polarity of permanent magnets 11 within a pair are inverse to each other. Directions of polarity of adjacent magnets 11 attached on a same side of the core are also inverse from one to the other. In other words, N poles are facing to each other through the core 10 in a pair, S poles are facing to each other through the core 10 in an adjacent pair, and so on. As a result, magnetic flux flows from N poles of the magnets 11 facing outwards (distal N poles) to S poles facing outwards (distal S poles) of adjacent magnets 11 passing through a space therebetween. Magnetic flux flows from the distal S poles to proximate N poles of the same magnet at which the magnet 11 is connected to the core 10 (proximate N poles) through the magnet itself, and flows from the proximate N poles to adjacent proximate S poles passing through the core 10, as shown by dotted lines in FIG. 13.